1. Field of the Invention
The present invention relates to a suction unit which makes it possible to transport a workpiece by attracting a workpiece with a suction pad and linearly reciprocate the workpiece along a body by a driving source.
2. Description of the Related Art
A fluid pressure cylinder is used for a suction unit for attracting and transporting the workpiece such as a semiconductor chip. Such a fluid pressure cylinder transports a workpiece attracted by a suction pad under the action of a pressure fluid.
A piston is displaced in the axial direction by the pressure fluid which is supplied from one port of the fluid pressure cylinder. A piston rod integrally connected to the piston is displaced in the axial direction. During this process, the suction pad attached to one end of the piston rod abuts against the upper surface of the workpiece. The workpiece is attracted by the suction pad with the negative pressure of the fluid introduced through the interior of the hollow piston rod.
When the pressure fluid is supplied to the other port of the fluid pressure cylinder, the fluid pressure cylinder is displaced upwardly while attracting the workpiece and transports the workpiece.
In the suction unit with the conventional fluid pressure cylinder, the suction pad attracting the minute workpiece such as the semiconductor chip is displaced in the axial direction by the pressure fluid which is supplied to the fluid pressure cylinder. As a result, the piston disposed in the fluid pressure cylinder is driven by the pressure fluid. Therefore, it is difficult to adjust the speed of the suction pad when the suction pad abuts against the upper surface of the workpiece. For this reason, impact may be excessive when the suction pad abuts against the workpiece, and load excessive enough to break the workpiece may be applied thereto.